An effective immune response is initiated by T-cells of the immune system being activated, with this activation being induced by an antigen or mitogen. The activation of the T-cells requires a large number of cellular changes, including, for example, the expression of cytokines and their receptors. These cytokines include, inter alia, IL-15 and IL-2. These interleukins are known growth factors which play a significant role in the proliferation and differentiation of human and murine T-cells, macrophages, natural killer (NK) cells, cytotoxic T-cells (CTL), and lymphocyte-activated killer (LAK) cells as well as in the co-stimulation of B cells which have been activated, for example, by anti-immunoglobulin (anti-IgM) or phorbol esters. The proliferation of these cells augments the immune response of an organism.
In a large number of diseases, it is necessary, for therapeutic reasons, to suppress a response of the patient's immune system. These diseases include, for example, autoimmune diseases, in particular diabetes mellitus type I, rheumatoid arthritis, multiple sclerosis, chronic liver diseases, inflammatory intestinal diseases, graft-versus-host disease and transplant rejection. One therapeutic approach is that of using immunosuppressants, in particular antagonistic IL-15 or IL-2 antibodies, or IL-15 or IL-2 antagonists, to suppress the humoral or the cellular immune response.
The above-described IL-15 antagonists are mutated IL-15 (mut-IL-15) sequences which achieved antagonistic effects either on their own or as fusion proteins. These fusion proteins are polypeptides which consist of a N-terminal mut-IL-15 fragment and a C-terminal Fc fragment, in particular a murine IgG2a or human IgG1 (see, e.g., WO 97/41232; WO 2004/035622; Kim, Y. S., et al., J. Immunol. 160 (1998) 5742-5748).
In general the IEP-values (isoelectric point, pI) of proteins are important characteristics for ion exchange chromatography of proteins. Below the IEP proteins gain a positive net charge and can be chromatographed on cation exchangers, above the pI they have a negative net charge and anion exchangers should be used (see e.g. New comprehensive biochemistry, Neuberger, A., and van Deenen, L.L.M. (eds.), Volume 8, Separation Methods, Deyl, Z. (ed.), Elsevier Science Publishers B.V. (1984) page 247).
Conjugated Factor VIII molecules are reported in WO 2009/108806. In US 2009/0304669 a preparative purification process for human furin is reported. A chromatography purification of antibodies is reported in US 2009/270596. In WO 2009/074634 is reported a composition for pulmonary delivery. Polypeptides, antibody variable domains and antagonists are reported in WO 2008/149147. In US 2008/177048 an enhanced capacity and purification of antibodies by mixed-mode chromatography in the presence of aqueous-soluble non-ionic organic polymers is reported. Refolding of recombinant proteins is reported in US 2008/008975. In US 2007/167613 a process for purification of antibodies is reported. Antibody purification is reported in US 2007/112178. Purified immunoglobulin fusion proteins and methods of their purification are reported in WO 2009/111347.
Aldington et al. (J. Chrom. B 848 (2007) 64-78) report the scale-up of monoclonal antibody purification processes. Pilot scale purification of human monoclonal IgM (COU-1) is reported by Tornoe at al. (J. Immunol. Meth. 205 (1997) 11-17). In US 2010/069617 enhanced protein aggregate removal by mixed-mode chromatography on hydrophobic interaction media in the presence of protein-excluded zwitterions is reported.